In the case of normal chip cards which are widely used, for example in electronic payment transactions, the communication between the chip located on the chip card and a reader is contact-based, i.e. via chip card contacts exposed toward the outside of the chip card. For this purpose, however, the chip card must always be singled out when used and introduced into a corresponding reader which may be considered to be disruptive by a user. An interesting extension which solves the problem is offered by so-called dual interface chip cards in which the chip can also communicate by means of a contactless interface in addition to the normal contact-based interface. The contactless interface on the chip card can have a chip card antenna which is contained in the chip card and connected to the chip. The chip card antenna and the chip can be arranged conjointly on a chip card module wherein such a miniaturized form of the chip card antenna can then be called a chip card module antenna. Independently of the type of chip card antenna, an electrical connection is formed between it and the chip card module or the chip, respectively.
In the case of electronic payment systems, for example, a functional distance of up to 4 cm is required between the chip and the reading unit. However, meeting this target specification may be found to be problematic since it may not be possible in some cases to arrange a sufficiently large chip card module antenna on the small surface available on the chip card module for wireless communication to take place at the required distance. In order to improve the wireless communication capability, a further antenna can be provided in addition to the chip card module antenna, namely an amplifier antenna or booster antenna. The booster antenna can be provided on a separate layer and contained in the chip card. The separate layer which contains the booster antenna can be laminated into the chip card, for example, during its production.
In the case of chip card antennas which are not arranged on the chip card module and therefore have in most cases an adequate size, the use of a booster antenna can be omitted. When completed chip card bodies are equipped with chip card modules, however, the chip card must then be milled precisely so that the contacts provided on the chip card module can be positioned over corresponding contacts of the chip card antenna. The contacts can then be joined together by means of an adhesive, supplying pressure.
The production process described above is costly and complex. In addition, the contact locations between chip card module and the chip card antenna can have little mechanical ruggedness and may become detached in the case of bending and folding processes to which chip cards can be exposed in everyday use. Having regard to these problems, the expected life of a chip card having a chip card antenna may be two years. In general, a far longer life of, for example, ten years would be desirable, for instance when such chip cards are used in governmental facilities where the costs of exchanging or renewing due to the volume of chip cards used could be saved.
To avoid the problems of the mechanically susceptible electrical connection with the chip card module or the chip, respectively, existing in the case of large-format chip card antennas, booster antennas are coupled inductively to chip card module antennas. Normal booster antennas extend in most cases over the entire surface of the chip card, if necessary also over part-areas which are provided, for example, for lettering embossed in the chip card (embossing areas, defined, for example, in ISO/IEC 7811-1 Standard) or are provided for the chip cavity so that such chip cards are basically not ISO/IEC-compliant. Furthermore, there has hitherto not been any optimization of the booster antenna in chip cards with regard to their electrical parameters so that such chip cards cannot be certified, for example, according to the EMVCo Standard—a global standard for credit and ATM cards on the basis of chip card technology.